The present invention relates to a cassette type semiconductor memory device to be coupled to the main frame of a data processor through a connector.
In recent years, semiconductor memory devices of the cassette type have frequently been used as external memory devices or auxiliary memory devices for extending the capacity of the main memory in small data processors, such as personal computers. This type of memory device is provided with a semiconductor memory device, such as a ROM or a RAM, which device is contained in a cassette. The memory device is called a ROM pack or a RAM pack (and, generally, a memory pack), according to the type of semiconductor memory device used. The memory pack is removably attached to the main frame through a connector.
The ROM pack is of the nonvolatile type, thus requiring no battery pack-up. On the other hand, the RAM pack is of the volatile type, requiring a battery back-up. Due to this feature, the RAM pack cannot be inserted into or removed from the main frame, while the power source of the main frame is in an ON state. In other words, the so-called live-line (or active-line) insertion/removal of the RAM pack is not allowed. The reason for this is that, if the connector pins of the memory pack are slantly placed with respect to the connector sockets of the main frame, it is not possible to insert or remove the connector pins of the memory pack into or away from the connector sockets of the main frame all at a time. As a result, the data in the memory device is erased or changed by an erroneous memory access with an imperfect connection of the power source or ground.
To cope with this problem, the lengths of the connector pins are made to differ according to the kind of the power source and signals, thereby to forcibly set up the order of the insertion/removal of the pins into and away from the sockets. Another approach to this problem is to sense the insertion/removal of the memory pack by means of a photosensor or the like, and to automatically turn off the power source of the main frame.
The former approach is expensive and impractical. Thus, the latter one is widely used at present. Therefore, the live-line insertion/removal of the memory pack, in a strict sense, has not been executed. In the latter approach, since the power source is forcibly turned off, the flow of job is interrupted.